1. Field of the Invention
The present invention relates to drawer type cooking devices belonging to built-in kitchen equipment such as microwave ovens built into furniture or cabinets, for example.
2. Description of the Related Art
There has been proposed in the prior art, cooking devices, each having a drawer body formed integrally with a door capable of being drawn out to the front side of the cooking device. Such drawer type cooking devices are suitably applied to designed kitchens where a plurality of cooking devices are arranged three-dimensionally, since they can be built into the area below the kitchen countertop without occupying the space above the countertop. Therefore, drawer type cooking devices are characterized as cooking devices suitably applied to fitted kitchens or designed kitchens, and the use thereof is recently spreading widely, especially in the United States.
The present applicant has proposed one example of a drawer type microwave oven in Japanese patent application laid-open publication No. 2006-223336 (patent document 1), disclosing a drawer type cooking device comprising a cooking device body having a heating chamber, a drawer body disposed movably in the cooking device body and capable of being drawn out to the exterior from within the heating chamber of the cooking device body, and slide rails for moving the drawer body within the cooking device body, wherein the slide rails are disposed on the exterior of the heating chamber so as to enable the slide mechanism to be formed without using members or materials having high heat resistance and frame resistance, and also to prevent the occurrence of discharge failures caused by microwave.
Safety standards for microwave ovens are established in the respective countries, but in the United States which has a model safety standard for such respective standards, safety standards UL 923 related to microwave ovens have been established as UL (Underwriter's Laboratories) standards. According to UL 923, it is necessary that the microwave oven does not cause microwave leakage when the door is at a closed state, and in addition, it is also necessary that microwave leakage from the heating chamber does not occur even during an abnormal state of use where external force or foreign objects are applied to the microwave oven without using any tools during the heating operation using microwave (electromagnetic wave with a frequency of about 2450 MHz).
One of the test conditions for confirming that the microwave oven conforms to the UL standards related to microwave leakages include a condition in which a horizontal torsional force is applied to the door during heating operation in such a range that the supply of microwave is not stopped. In drawer type microwave ovens, latches for controlling the main switch of the microwave generation device are disposed at two locations on left and right sides of the microwave oven as gap detection means, but since much weight is put on the visual appearance and design of the front side of the cooking device body when the door is opened, these latches are disposed at deep areas within the cooking device body. In the case of drawer type cooking devices, for example, the door is designed to be opened electrically when the main switch disposed on the left side thereof is turned off. However, according to the test condition described above, the door is opened while applying torsional force to the door, and only the main switch disposed on one side is turned on. In other words, when a user attempts to open the door by holding only the right end side of the door handle, only the right side of the door starts to open with the left side of the door still closed, and the latch will only move sideways with the main switch still continued to be switched on, so that the operation of the cooking device, that is, the operation of the microwave generating device, will not stop. As a result, microwave leakage will occur from the gap formed at the partially opened door.
The above-described test for confirming whether microwave leakage occurs under such condition will hereinafter be referred to as “jerk microwave leakage test” for sake of convenience in the present application. In the case of a door so-called an open handle door that can be gripped both via ordinary gripping and backhand gripping, by each hand, the user can grasp at almost any place on the handle; so, the manual “leverage” thus applicable to the door can be significant, making it likely to have twisting displacement of the door enough to cause jerk microwave leakage. However, if the latch structure is designed to have a high sensitivity so that the latch activates even by a slight displacement and the main switch of the microwave generation device is turned off in order to avoid such leak from occurring, the latch may activate erroneously even when a slight shock is applied to the device during heating operation and the heating operation will be discontinued, according to which latch alignment becomes difficult and the productivity of the microwave oven is deteriorated. Furthermore, since the stress such as the door opening and closing operation during use may cause the sensitivity of the latch to vary with time, such a sensitive latch structure is not preferable from the viewpoint of product reliability.
In widely used microwave ovens disposed on countertops, the doors open and close either in the horizontal or vertical direction via a hinge, and when a horizontal torsional force is applied to open the door by the user holding one end of the door during heating operation, the latch is released immediately and the supply of microwave is stopped instantly. Therefore, such widely used microwave ovens do not have difficulty in satisfying the jerk microwave leakage test standards.
On the other hand, according to drawer type microwave ovens, when the opening of the door is detected via the left and right latches disposed on the heating chamber, the supply of microwave is stopped immediately, but when a door opening force biased to one side is applied to the door, the detection operation of the latch is dispersed among respective microwave ovens depending on specific product structures, and the operation becomes uncertain. Therefore, unlike the microwave ovens adopting the above-mentioned hinge structure, it is important for drawer type microwave ovens that the jerk microwave leakage test is performed both at the time of designing the product and at the time of test production.
According to the drawer type microwave oven disclosed in patent document 1, the drawer body with a door is movably disposed via a slide mechanism constituting a movement mechanism disposed at three locations, at both left and right side walls and the bottom wall at the outer side of the heating chamber within the cooking device body, for automatically opening and closing the door. However, in order to absorb the mutual dimensional dispersion of the drawer body and the heating chamber during production, the dimensional relationship of the drawer body and the heating chamber is set so that when the drawer body is stored in the heating chamber, a predetermined clearance is formed between the drawer body and the walls of the heating chamber at horizontal direction and at the bottom, excluding the upper area which is opened to enable food to be taken into and out of the heating chamber.
According to the drawer type microwave oven disclosed in patent document 1, when external force is applied to the drawer body, in order to prevent the drawer body from moving the distance corresponding to the clearance and to prevent the outer side of the drawer body from directly colliding against the inner side of the heating chamber, multiple pairs of roller-shaped shock absorbing members are axially supported rotatably on the outer side of the leading end of the drawer body (the depth side corresponding to the storing direction of the drawer body) so as to relieve the impact and to realize a sliding movement with respect to the inner side of the heating chamber.
The multiple pairs of shock absorbing members are arranged so that at least one pair of lower shock absorbing members are axially supported horizontally via a rotation axis near the bottom surface of the drawer body so as to realize the shock absorbing operation in the lower direction and to enable sliding movement, and another at least one pair of side shock absorbing members are axially supported perpendicularly above the lower shock absorbing members via a rotation axis so as to realize the shock absorbing operation in the side direction and to enable sliding movement.
According further to the prior art drawer type microwave ovens, the side shock absorbing members are disposed near the center in the vertical direction of the side panels of the heating chamber, and when collision occurs to the side walls of the heating chamber placed adjacent to the side shock absorbing members, the side walls are elastically deformed so as to relive the stress applied to the side shock absorbing members. In other words, the reliability of the arrangement is improved by adopting an arrangement where the side walls of the heating chamber are deformed by receiving stress, so that the areas of the side wall panels of the heating chamber corresponding to the fixing positions of the side shock absorbing members are designed so as not to have components secured thereto via welding, screw engagement and so on.
According to the prior art drawer type microwave oven with shock absorbing members, when horizontal torsional force is applied to extreme end portions such as the end of the door of the drawer type microwave oven or the end of the door handle, a horizontal rotational moment pivoting around a vertical axis is applied to the drawer body, and in that state, the drawer body applies pressure via the shock absorbing member to the side panel of the heating chamber on the side where the drawer body approximates the inner side of the side panel of the heating chamber. When the side panel of the heating chamber elastically deforms in response to this pressure, the drawer body moves in pivoting motion, and when the door is at a closed state, a biased gap is formed between the front panel of the heating chamber and the inner side of the door as a result.
When the drawer body moves in such a manner to create a biased gap in one direction, since the latch will not activate until the gap widens to a certain degree and the supply of microwave will not stop, microwave leakage is likely to occur through the gap. As a result, the structure of the drawer type microwave ovens may not satisfy the standards of the jerk microwave leakage test.
As described, in order to prevent the occurrence of microwave leakages in a jerk microwave leakage test when horizontal torsional force is applied to the door, it is necessary to prevent gaps from occurring between the front panel of the heating chamber and the inner side of the door.
Therefore, when the thickness of components constituting the heating chamber is reduced with the aim to reduce the weight and cost of the product, even if the mechanical strength of the heating chamber composed of the thin components satisfies a sufficient safety factor, microwave leakage may occur by the elastic deformation of the side panel of the heating chamber during the jerk microwave leakage test. There is a drawback that the occurrence of such microwave leakage makes it impossible to reduce the thickness of the components constituting the heating chamber.
One possible solution of the problem is to reduce the thickness of the components constituting the heating chamber while enhancing the rigidity of the side panels of the heating chamber so as to prevent elastic deformation of the side panels, but if reinforcements are added to the components constituting the heating chamber, the cost-reduction effect by the reduction in thickness of the components constituting the heating chamber is diminished, and in some cases, the cost is even increased, so that solutions other than adding reinforcements and increasing the number of components are desired.
Furthermore, since drawer type cooking devices are generally disposed at positions closer to the floor surface compared to general cooking devices, they are distanced from the view of the user, and in actual use, the user may bump against the drawer body when the door is at a opened state, and a strong shock may be applied to the user if the drawer body is supported with high rigidity. Therefore, from the viewpoint of safety, it is not preferable to increase the rigidity of the side panels of the heating chamber by increasing the plate thicknesses thereof.
Moreover, the door handle has a protruded circular-arc shape, so that the user can perform pulling and pushing operations by gripping only the center area since there is a sufficient clearance formed between the handle and the front side of the door at the center, but at both ends the handle approximates the front side of the door so as not to enable the user to grip the ends, according to which torsional force can be prevented from being applied easily to the door during the jerk microwave leakage test. Therefore, the user may feel inconvenience since the handle gripping area is restricted to the center area even when the width of the drawer type microwave oven is very large.
Since the door handle of a drawer type cooking device is subjected to such significant restrictions, even if a door handle design simply extending linearly in the horizontal direction is preferred from the viewpoint of coordination to unify and integrate the interior design of the whole kitchen, such handle design cannot be adopted in a product if the device does not conform to the jerk microwave leakage test. As a result, drawer type microwave ovens are not adopted in the above-mentioned type of interior designed kitchens, and therefore, the widening of sales volume is inhibited. Thus, a solution is desired for preventing the occurrence of microwave leakages during the jerk microwave leakage test even when the design of the door handle is selected to be coordinated with the kitchen interior design.
As described, the problem to be solved in drawer type cooking devices is to provide a drawer type cooking device having an outer casing, an inner casing fit to the interior of the outer casing and constituting a heating chamber having a front side opened, a drawer body having an integrally disposed door for opening and closing the opening of the heating chamber and capable of moving into and out of the heating chamber via a slide mechanism, and a shock absorbing member for preventing the outer side of the drawer body from directly colliding against the inner side of the heating chamber, wherein the areas opposed to the shock absorbing members of the side wall panels of the inner casing constituting the heating chamber are reinforced using existing components.
The object of the present invention is to provide a drawer type cooking device having reduced the thickness of the components constituting the heating chamber, capable of reinforcing the inner casing without additionally providing reinforcement members to the components constituting the heating chamber, which had led to increase of number of components and manufacturing costs.